This invention relates generally to a device for effecting a gastight closure of an inner tube of a hollow electrode of an electrothermal smelting furnace, and more particularly to such a device as having a deformable closure plug which can be introduced into the inner tube from a position inside a stub tube attached to the inner tube in which it is clear of the flow path through the inner tube. The plug can be introduced by means of an actuator rod and can be forced against the wall of the tube to make a seal by application of pressure to the actuator rod.
Hollow electrodes through which electrothermal smelting furnaces are charged with a particulate load, must be lowered at certain intervals of time, depending upon the consumption in the arc, and must be replaced at the top end by another electrode section. Such a section is, as a rule, about 2 meters long. The electrode section comprises sections of an outer sheet steel sheath and of the inner feed tube, the annular space bounded by these being filled with an electrode compound. During attachment of a new electrode section and the necessary interruption of the feeding of the load, in order to prevent escape of poisonous gases, in particular carbon monoxide, through the hollow electrode, the inner tube of the hollow electrode must be closed in a gastight manner. Temporary closure of the inner tube of the hollow electrode may, however, also be necessary when disturbances occur in the operation of the furnace or when repair work must be performed on the hollow electrode.
Regarding a known closure device of the type described, a closure is mounted on the top end of the inner tube of the hollow electrode. The inner tube has a stub at the side for feeding in the load and a stub tube is provided coaxially with the inner tube of the hollow electrode to receive the closure plug in the non-actuated state. If, during the shut-off procedure, the closure plug is slid by means of the actuator rod into the inner tube of the hollow electrode up to a seat, against a stop moved into the inner tube, and is caused, for example by application of pressure to the actuator rod, to enlarge in cross-section, it shuts off the inner tube so that the tube is gastight.
The considerable disadvantage of this known device consists in the fact that a large stroke is necessary for actuation of the shut-off plug and, in addition to the space necessary for the electrode section which is subsequently to be added on, space must also be available above the hollow electrode for the closure device as well as for mounting it on the renewed inner tube of the hollow electrode. The known device also requires a relatively large expenditure of effort, because, depending upon the form of the closure plug, before addition on a new electrode section either the actuator rod must be attached from the closure plug in its sealing position in order to be able to take away the closure, or the actuator rod must, upon removal of the closure, in some way or another be kept under stress. Finally the structural size is also increased by the form and arrangement of the movable stop in the inner tube of the hollow electrode.